ANSTO :: Browsing by Author "Iles, GN"

Browsing by Author "Iles, GN"

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Boson peak in ultrathin alumina layers investigated with neutron spectroscopy
(American Physical Society, 2020-06-11) Cortie, DL; Cyster, MJ; Ablott, TA; Richardson, C; Smith, JS; Iles, GN; Wang, XL; Mitchell, DRG; Mole, RA; de Souza, NR; Yu, DH; Cole, JH
Bulk glasses exhibit extra vibrational modes at low energies, collectively known as the boson peak. The vibrational dynamics in nanoscale alumina glasses have an impact on the performance of qubits and other superconducting devices; however, the frequency of the boson peak has not been previously measured. Here we report neutron spectroscopy experiments on Al/Al2O3 nanoparticles consisting of spherical metallic cores with a radii from 20 to 1000 nm surrounded by a 3.5-nm-thick alumina glass. A low-energy peak is observed at ωBP = 2.8 ± 0.6 meV for highly oxidized particles, indicating an excess in the density of states. The intensity of the peak scales inversely with particle size and oxide fraction, indicating a surface origin, and is redshifted by 3 meV with respect to the van Hove singularity of γ -phase Al2O3 nanocrystals. Molecular-dynamics simulations of α-Al2O3, γ -Al2O3 and α-Al2O3 show that the observed boson peak is a signature of the ultrathin glass surface and the characteristic frequency is reduced compared to the peak in the bulk glass. © 2020 The Authors. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license.
Crystal field excitations for Ho3+ in HoFeO3
(Australian Institute of Physics, 2017-01-31) Stewart, GA; Iles, GN; Mole, RA; Yamani, Z; Ryan, DH
The orthoferrites, RFeO3 (R = rare earth), are promising candidates for innovative spintronic applications. HoFeO3 is of particular interest because optical measurements indicate that the magnetic splitting of the Ho3+ ion’s crystal field (CF) ground state lies in the range of antiferromagnetic–resonance frequencies for the Fe subsystem [1]. Inelastic neutron scattering data recorded on the Australian Neutron Beam Centre’s PELICAN time-of-flight spectrometer are consistent with Ho3+ CF levels at about 10.5, 15.4 and 22.0 meV. Additional low energy transitions (< 1 meV) exhibit behaviour that groups into three distinct temperature ranges (Fig. 1). Given that the Fe sub-lattice undergoes magnetic reorientation over the temperature range of 35 K to 60 K, it is believed that these excitations are associated with magnetic splitting of the Ho3+ ground CF level due to an exchange field originating from the Fe sub-lattice.
Data-processing technique for the Taipan “Be-filter” neutron spectrometer at the Australian Nuclear Science and Technology Organisation
(American Institute of Physics (AIP), 2021-07-09) Iles, GN; Rule, KC; Peterson, VK; Stampfl, APJ; Elcombe, MM
There are five filter-analyzer neutron spectrometers available worldwide for scientists to use in order to measure the vibrational density of states in various samples. While Taipan, the thermal spectrometer, has been operated as a triple-axis spectrometer at the Australian Centre for Neutron Scattering since 2010, a beryllium filter analyzer spectrometer was added in 2016. Due to the complex nature of the data post-processing, it has thus far been impossible to fully treat experimental data from scientific measurements taken over the last five years. We have successfully created a robust method of treating data from the Taipan filter-analyzer and present the method on three different samples. The data-treatment process includes correction for the non-linear energy variation of a particular monochromator, removal of higher-order wavelength contamination, and estimation of low-energy multiple-scattering. The steps described here can be utilized by all users of the Australian Nuclear Science and Technology Organisation “Be-filter”—past, present, and future. © 2021 Author(s). Published under an exclusive license by AIP Publishing.
Determination of the crystal field levels in TmV2Al20
(Australian Institute of Physics, 2017-01-31) White, R; Hutchison, WD; Iles, GN; Mole, RA; Cadogan, JM; Namiki, T; Nishimura, K
Recent interest in so called caged rare earth compounds of the RM2Al20-type (R = lanthanide, M = transition metal) follow from their fascinating physical and magnetic properties at low temperatures. Recent work on PrV2Al20 and PrTi2Al20 revealed unusual phenomena, including a quadrupolar Kondo effect and superconductivity, brought about by the cubic symmetry of the Pr3+ site inducing a non-magnetic ground state in the ion. As a hole analogue of the PrV2Al20 compound, TmV2Al20 has been investigated for equivalent heavy Fermion behaviour at low temperatures. In previous work, specific heat and magnetisation data were modelled with the crystal field parameters W = 0.5 K and x = -0.6 based on the Lea, Leask and Wolf formalism. However, the experimental zero field specific heat near 0.5 K could only be matched in the modelled curves using an artificial ground state broadening. In this work inelastic neutron scattering data obtained from the PELICAN time of flight spectrometer located at the OPAL reactor, Lucas Heights has allowed further refinement of the values to W = 0.42(1) K and x = -0.63(1). In addition the CEF transitions are found to be very broad, as required for the specific heat, and suggestive of strong 4f-conduction electron coupling.
Determination of the crystal field levels in TmV2Al20
(Australian Institute of Nuclear Science and Engineering, 2016-11-29) White, R; Hutchison, WD; Iles, GN; Mole, RA; Cadogan, JM; Nishimura, K
There has been increasing interest in compounds of the RM2Al20-type (R = lanthanide, M = transition metal) in recent years due to the unique physical and magnetic properties many have been shown to display at low temperatures. Recent work carried out on PrV2Al20 and PrTi2Al20 has revealed a number of interesting phenomena, including a quadrupolar Kondo effect [1, 2] and superconductivity [3, 4] brought about by the cubic symmetry of the Pr3+ site inducing a non-magnetic ground state in the ion. As a hole analogue of the PrV2Al20 compound, TmV2Al20 has been investigated to see whether it too displays such phenomena at low temperatures. Crystal field calculations based on specific heat and magnetisation have been carried out previously [5] with parameters W = 0.5 K and x = -0.6 determined based on the Lea, Leask and Wolf formalism [6]. These results have been further refined to W = 0.42(1) K and x = -0.63(1) using inelastic neutron scattering data obtained from the PELICAN time-of-flight spectrometer located at the OPAL reactor, Lucas Heights.
Determination of the crystal field levels in TmV2Al20
(International Conference on Neutron Scattering, 2017-07-12) White, R; Hutchison, WD; Iles, GN; Mole, RA; Cadogan, JM; Namiki, T; Nishimura, K.
So called caged rare earth compounds of the RM Al20-type (R = lanthanide, M = transition metal) exhibit interesting physical and magnetic properties at low temperatures. For example PrV Al20 and PrTi Al20 show a quadrupolar Kondo effect [1] and superconductivity [2] brought about by the non-magnetic ground state and the cubic symmetry of the Pr3+site. In this work the compound TmV Al20, a hole analogue of PrV Al20 has been investigated. Previous crystal field calculations based on specific heat and magnetisation [3] resulted in parameters of W = 0.5 K and x = -0.6 within the Lea, Leask and Wolf formalism [4]. However to match the experimental zero field specific heat near 0.5 K, an artificial broadening of the ground state was applied. To validate and clarify these results, we have carried out an inelastic neutron scattering experiment on the PELICAN time-of-flight spectrometer to determine the energy splitting between the crystal field levels. This has allowed a further refinement of the crystal field parameters to W = 0.42(1) K and x = -0.63(1). The very broad Lorentzian line shapes suggest strong 4f-conduction band electron coupling.
Determination of the crystal field levels in TmV2Al20
(Australian Institute of Physics, 2018-01-31) Hutchison, WD; White, R; Stewart, GA; Iles, GN; Mole, RA; Cadogan, JM; Namiki, T; Nishimura, K
The interest in compounds of the RM2Al20-type (R = lanthanide, M = transition metal) in recent years reflects the fascinating physical and magnetic properties on display at low temperatures. For example, in PrV2Al20 and PrTi2Al20 the phenomena reported include a quadrupolar Kondo effect [1] and superconductivity [2]. Central to such systems is the cubic symmetry of the Pr3+ site inducing a non-magnetic ground state in the ion. As a hole analogue of the PrV2Al20 compound, TmV2Al20 has been investigated in the hope of observing similar phenomena at low temperatures. At last year’s ‘Wagga’ we reported that we had determined the Tm3+ crystal field parameters W = 0.42(1) and x = -0.63(1) [3] (based on the Lea, Leask and Wolf formalism [4]) for TmV2Al20 using inelastic neutron scattering on PELICAN at the OPAL reactor, Lucas Heights. However, the line shapes found were extremely broad Lorentzians, indicative of a coupling of crystal field states to conduction electrons, ‘smearing out’ the energy required for transitions. Here, we report more recent developments: Tm3+ electron spin resonance results together with modelling of physical properties lead to the conclusion that there is a small local distortion away from cubic symmetry.
Does the boson peak survive in an ultrathin oxide glass?
(arXiv.org, 2019-07-29) Cortie, DL; Cyster, MJ; Smith, JS; Iles, GN; Wang, XL; Mitchell, DRG; Mole, RA; de Souza, NR; Yu, DH; Cole, JH
Bulk glasses exhibit extra vibrational modes at low energies, known as the boson peak. The microscopic dynamics in nanoscale alumina impact the performance of qubits and other superconducting devices, however the existence of the boson peak in these glasses has not been previously measured. Here we report neutron spectroscopy on Al/Al2O3−x nanoparticles consisting of spherical metallic cores from 20 to 1000 nm surrounded by a 3.5 nm thick alumina glass. An intense low-energy peak is observed at ωBP = 2.8 ± 0.6 meV for highly oxidised particles, concurrent with an excess in the density of states. The intensity of the peak scales inversely with particle size and oxide fraction indicating a surface origin, and is red-shifted by 3 meV with respect to the van-Hove singularity of γ-phase Al2O3−x nanocrystals. Molecular dynamics simulations of α-Al2O3−x, γ-Al2O3−x and a-Al2O3−x show that the observed boson peak is a signature of the ultrathin glass surface, and the frequency is softened compared to that of the hypothetical bulk glass.
EMU, the backscattering spectrometer at the Australian Centre for Neutron Scattering
(International Conference on Neutron Scattering, 2017-07-12) Iles, GN; de Souza, NR; Klapproth, A
The cold-neutron backscattering spectrometer, EMU, one of the four spectrometers at ANSTO, received its operating licence in 2016. First spectra were obtained from measurements on laboratory standards such as polyethylene, m-Xylene and ammonia perchlorate [1]. The high energy resolution of EMU allows dynamics in the nanosecond timeframe to be observed. This high resolution is due to backscattering from the Si (111) crystal monochromator and analyser arrays, delivering a spectrometer FWHM energy resolution in the order of 1.2µeV. EMU also features a linear Doppler drive modulating incident neutron energies over ± 31 µeV. Scattered, analysed neutrons are counted in 3He LPSD arrays. By setting the Doppler-driven backscattering monochromator to zero motion, elastic fixed window scans (EFW) can be performed. Changes in intensity of the analysed neutrons,with changing temperature, for example, correspond to changing dynamics in the system. Alternatively, when the incident energy is modulated, quasi-elastic neutron scattering (QENS) can be used to observe changes in the profile shape of the elastic peak. Finally, EMU can be used to observe purely inelastic scattering, such as observed in samples exhibiting rotational tunnelling. Future work will involve developing MANTID software for data treatment and analysis, and continuing to improve the signal-to-noise ratio.
EMU, the cold-neutron backscattering spectrometer at the Bragg Institute, ANSTO
(Australian Institute of Physics, 2015-02-03) de Souza, NR; Klapproth, A; Iles, GN
The Bragg Institute is currently in the final installation stage of a cold-neutron backscattering spectrometer in the ANSTO OPAL research reactor neutron guide hall. This spectrometer, called EMU, is based on Si (111) crystal backscattering and extracts neutrons from a cold neutron guide via a double HOPG (002) crystal premonochromator setup. Backscattering occurs through implementation of spherical focusing between the Si (111) crystal monochromator and analyser arrays, aiming to deliver a spectrometer FWHM energy resolution in the order of 1.2 μeV. EMU also features a 7-metre long focusing guide located between the two premonochromators, a so-called graphite chopper alternating beam delivery to the backscattering crystal monochromator and then into the secondary spectrometer, and a linear Doppler drive modulating incident neutron energies over ± 31 μeV. Scattered, analysed neutrons are counted in 3He LPSD arrays. EMU is provisioned for future extensions of its dynamic range via higher-resolution, undeformed Si (111) crystal analyser arrays, and variable HOPG (002) crystal premonochromator reflection angles. Access to the EMU spectrometer will be via beam-time requests to the OPAL neutron-beam user facility. EMU is ideally suited for measuring relaxation times from a few 10 ps to over 1 ns, for momentum transfers up to 2 Å-1, and readily from cryogenic temperatures up to 700 K.
EMU, the high resolution backscattering spectrometer at ANSTO
(Australian Institute of Nuclear Science and Engineering, 2016-11-29) de Souza, NR; Klapproth, A; Iles, GN
The energy range and resolution of backscattering spectrometers are well suited to characterizing relaxations on an atomic and molecular scale, such as diffusion processes occurring in e.g. polymer chains, membranes, proteins, molecular crystals, between interstitial crystal lattice sites. The EMU spectrometer can be used to study the dynamics of water molecules in the confined space of a host structure or ionic diffusion in conductor materials. In addition, quantum rotational tunnelling of functional groups (e.g. -CH3, -NH4) and hyperfine splitting of nuclear energy levels can be investigated. Relaxation times from a few 10 ps to over 1 ns are accessible. We will present the first -CH3 tunneling and diffusional motion spectra, obtained during the instrument commission, as an example of EMU’s present capabilities. The experiments have been performed in a temperature range from 3 – 650K, using top- and bottom-loading cryo furnaces. Other sample environments such as pressure, magnetic fields, controlled gas delivery systems, sub-K cryostats etc. are also available or currently under testing. EMU entered user service in 2016 and we welcome proposals in a wide range of scientific disciplines. The EMU instrument has the highest energy resolution of the neutron spectrometers at ANSTO and provides a momentum transfer range from as low as 0.1 Å-1 up to 1.95 Å-1. The high energy resolution is obtained by neutron backscattering, which occurs twice, through spherical focusing onto the sample, located between the Si (111) crystal monochromator and the analyser arrays [1]. A linear Doppler drive modulates the incident neutron energies over an energy range of ± 31 µeV. The inelastic scattered neutrons are counted in two 3He linear-position sensitive detector arrays.
First spectrum measured on EMU, the cold-neutron backscattering spectrometer at the Bragg Institute, ANSTO
(Australian Institute of Physics, 2016-02-04) de Souza, NR; Klapproth, A; Iles, GN
The cold-neutron backscattering spectrometer, EMU, one of the four spectrometers at ANSTO received its commissioning licence in 2015. This allowed opening the neutron beam onto the instrument and after measuring nominal background radiation we made our first measurements with the instrument. EMU is based on Si(111) crystal backscattering and extracts neutrons from a cold neutron guide via a double HOPG (002) crystal premonochromator setup. Backscattering occurs through implementation of spherical focusing between the Si (111) crystal monochromators and analyser arrays, aiming to deliver a spectrometer FWHM energy resolution in the order of 1.2 μeV. EMU also features a 7-metre long focusing guide located between the two premonochromators, a so-called graphite chopper alternating beam delivery to the backscattering crystal monochromator and then into the secondary spectrometer [1] and a linear Doppler drive modulating incident neutron energies over ± 31 μeV. Scattered, analysed neutrons are counted in 3He LPSD arrays. We measured two samples, one a vanadium sample can and secondly a polyethylene sheet. Using event counting obtained from two temporarily placed 3He detector tubes, we were able to obtain a backscattered spectrum. It is critical to ensure that detected neutrons have been backscattered. Backscattered neutrons travel a further distance than those that scatter immediately at the sample and therefore the timing signal must be known accurately, to distinguish between spurious and actual data. Future work will involve developing MANTID software for data treatment and analysis.
First users on EMU, the cold-neutron backscattering spectrometer at the Australian Centre for Neutron Scattering
(Australian Institute of Physics, 2017-01-31) Iles, GN; de Souza, NR; Klapproth, A
The cold-neutron backscattering spectrometer, EMU, one of the four spectrometers at ANSTO, received its operating licence in 2016. First spectra were obtained from measurements on laboratory standards such as polyethylene, m-Xylene and ammonia perchlorate [1]. The high energy resolution of EMU, allows dynamics in the nanosecond timeframe to be observed. This high resolution is due to backscattering from the Si (111) crystal monochromator and analyser arrays, delivering a spectrometer FWHM energy resolution in the order of 1.2 geV. EMU also features a linear Doppler drive modulating incident neutron energies over ± 31 geV. Scattered, analysed neutrons are counted in 3He LPSD arrays. By setting the Doppler driven backscattering monochromator to zero motion, elastic fixed window scans (EFW) can be performed. Changes in intensity of the analysed neutrons, with changing temperature, for example, correspond to changing dynamics in the system. Alternatively, when the incident energy is modulated, quasi-elastic neutron scattering (QENS) can be used to observe changes in the profile shape of the elastic peak. Finally, EMU can be used to observe purely inelastic scattering, such as observed in samples exhibiting rotational tunnelling. The first users have now conducted experiments on EMU in a range of disciplines. We have measured the high temperature dynamics in lead-free ferroelectrics using (QENS) [2], and investigated the long-range oxygen diffusion in an ionic conductor [3]. We have also measured water diffusion in clays using (EFW) [4]. Future work will involve developing MANTID software for data treatment and analysis, and continuing to improve the signal-to noise ratio.
Hot carrier transfer processes in nonstoichiometric titanium hydride
(IOP Publishing, 2017-07-25) Wang, P; Iles, GN; Mole, RA; Yu, DH; Wen, X; Aguey-Zinsou, KF; Shrestha, SK; Conibeer, G
The absorber of the hot carrier solar cell (HCSC) needs to have a considerably reduced hot carrier thermalisation rate, in order to maintain the photo-generated hot carriers for enough time such that they can be extracted. The slow carrier cooling effect is predicted in materials in which the phononic band gap is sufficiently large to block the Klemens decay. Binary compounds with a large mass ratio between the constituent elements are likely to have large phononic band gap. Titanium hydride is one of these binary compounds that has the potential to become an absorber of the HCSC. Whilst a large phononic gap has been observed in stoichiometric TiH2, it has not been experimentally confirmed for hydrogen deficient TiH x (where x < 2). In this article, we report the phonon density of states of TiH1.65 measured using inelastic neutron scattering and presented to clearly show the phononic band gap. We also present the carrier thermalisation process of a TiH x (1< x <2) thin film by transient absorption, and estimate the carrier cooling time in this material. © 2017 The Japan Society of Applied Physics.
Hydrohalite formation in frozen clay brines
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Gates, W; Bordallo, HN; Ferhervari, A; Klapproth, A; Acikel, A; Bouazza, A; Aldridge, LP; Iles, GN; Mole, RA
Hydrated forms of cryosalts in frozen brines play important roles in the polar landscape and troposphere of Earth [1], and their melting [2] is implicated in recurring slope lineae (RSL) in Antarctica’s McMurdo Dry Valley [3] and equator-facing, mid-latitude (42ºN-52ºS) slopes of Mars [4]. Observation of the widespread occurrence of clay minerals and salts on the Martian surface [5] indicates that saline groundwater [6] may still be present on Mars. The surface of Mars ranges in temperature from 293 K on the equator at noon to 120 K at the poles and mobility of sub-surface water ice will depend on the local temperature and the mobility of confined water in the crustal clays. We applied quasielastic neutron scattering using the backscattering spectrometer EMU (Australian Nuclear Science and Technology Organisation) at 1 μeE resolution, to the system: sodium montmorillonite – 5M NaCl (Na-Mt-NaCl and calcium montmorillonite – 5M CaCl2 (Ca-Mt-CaCl2); to establish boundary conditions influencing the dynamics of confined water. Results from elastic fixed window (EFW) data indicate a substantial increase in the mean square displacement of hydrogen (H) in the brine conditions at all temperatures above 100K, indicating enhanced mobility of water in the presence of brines. A phase transition was observed in Na-Mt-NaCl at 255K (on heating) indicating the presence of the cryosalt hydrohalite (NaCl·2H2O), but no phase transition was observed in Ca-Mt-CaCl2. In addition, quasielastic neutron scattering (QENS) spectra highlighted that water in the Ca-Mt-CaCl2 system was strongly confined at room temperature. Recently [6] hydrohalite was observed to form in frozen gels of Na-Mt brines, but not in Ca-Mt brines. They considered that textural differences in the two forms allowed the gel pores of the Na-Mt to retain liquid saline pore water to well below the freezing point of pure water. Based on our analysis, water is restricted to rotational mobility in the Na-Mt-NaCl below 255K, but presents more translational mobility above 255K. These findings largely support those of Yesilbas [7] in the importance of pore structure in controlling cryosalt formation, and further implicate their role in associated phenomena such as RSL.
An inelastic neutron scattering investigation of holmium orthoferrite
(IOP Publishing, 2023-01-18) Stewart, GA; Iles, GN; Mole, RA; Yamani, Z
The inelastic neutron scattering spectra recorded in this study and elsewhere provide a useful set of crystal-field (CF) energy levels for the ground J = 6 term of Ho3+ in HoFeO3. The resolution of the low-energy, temperature-dependent pseudo-quadrupole ground state splitting and magnon peaks is consistent with the self-ordering of the Ho3+ sublattice at T Ho ∼ 8–10 K and supports earlier electron spin resonance investigations of the Ho3+ magnon behaviour. Systematic analysis of the grouped singlet CF levels of Ho3: HoFeO3, in conjunction with the CF Kramers doublet levels of the neighbouring Er3+: ErFeO3, has yielded possible sets of CF parameters for the two systems. © 2022 IOP Publishing Ltd.
Low-energy crystal field excitations observed using inelastic neutron scattering
(Australian Institute of Physics, 2016-02-02) Iles, GN; Stewart, GA; Mole, RA; Hutchison, WD; Cadogan, S
The time-of-flight spectrometer, PELICAN, at ANSTO operates two choppers which provide a fixed initial energy of neutrons to the sample. Configuring the instrument to a wavelength of 4.75Å, sets this initial neutron energy to 3.6meV. By phasing the choppers, however, harmonic wavelengths can be obtained such as λ/2, etc. By measuring a powder sample of ErNiAl4 at λ/2 (λ = 4.75Å) we could observe a greater range of positive energy transfers (to the sample) and, after appropriate background removal, confirm the presence of an excitation at 7meV. This excitation represents the emission from the crystal field level at 7meV to 0meV confirming the result obtained in a previous experiment.
Neutron scattering quantification of unfrozen pore water in frozen mud
(Elsevier, 2021-09) Gates, WP; Bordallo, HN; Bouazza, A; Carnero-Guzman, GG; Aldridge, LP; Klapproth, A; Iles, GN; Booth, N; Mole, RA; Seydel, T; Yu, DH; de Souza, NR
The Earth's polar regions are experiencing a greater frequency of freeze-thaw events throughout the polar summer, contributing to atmospheric methane and destabilising clay-rich sediments. Clays in soils tightly bind pore water and thus substantially modify freeze-thaw events. While temperatures of phase transitions for confined pore water may be precisely assessed using calorimetric or thermal analyses to −30 or −40 °C, neutron scattering directly probes how pores in clay minerals control ice formation and melting to lower temperatures. We apply elastic neutron scattering to accurately quantify the unfrozen water content of clay gels and unambiguously identify different pore-water environments by their freezing temperatures. Using this approach, we conclude that cryosuction controls water mobility in frozen soils in the absence of soluble salts to much lower temperatures than observed by other techniques. Dyanmics determined from neutron scattering indicates that water in clay gel pores thaws at much lower temperatures than currently considered, and thus pose potential risks for contaminant migration at sub freezing temperatures. The general poor strength of wet clays can significantly impact infrastructure in cold regions undergoing an increased frequency of freeze-thaw events. © 2021 Elsevier Inc.
PELICAN, the time-of-flight spectrometer at the Australian Centre for Neutron Scattering
(International Conference on Neutron Scattering, 2017-07-12) Iles, GN; Mole, RA; Yu, DH
The time-of-flight, direct-geometry neutron spectrometer, PELICAN, has been in the user program since 2014 at the OPAL research reactor, housed by the Australian Nuclear Science and Technology Organisation, ANSTO. The PELICAN instrument was designed to meet the diverse requirements of the Australian scientific community from physics, chemistry, material science, to biology. A wide range of research is covered including crystal-field excitations, phonon densities of states, magnetic excitations for various multifunctional materials including high Tc superconductors, novel magnetic, thermo-electric, ferroelectric and piezoelectric materials; molecular dynamics in hydrogen-bonded and storage materials, catalytic materials, cements, clays and rocks; and water dynamics in proteins and ion diffusion in membranes. PELICAN is located on a cold neutron guide with wavelengths in the range 2.4 Å to 6.3 Å (14.2 meV to 2.1meV), delivered by a specially designed and fabricated triple monochromators system, consisting of three banks of highly-oriented pyrolytic graphite (HOPG)crystals [1]. Combined with high speed Fermi choppers, an energy resolution of 50 µeV to 800 µeV has been achieved at the elastic line, while energy resolution at the desired energy transfer can be optimised through time focusing by adjusting the speed of the Fermi chopper.
PELICAN: cold-neutron time-of-flight spectrometer at the Australian Centre for Neutron Scattering
(Australian Institute of Physics, 2017-01-31) Iles, GN; Mole, RA; Yu, DH
PELICAN is a cold neutron time-of-flight neutron spectrometer located at the OPAL reactor within the Australian Centre for Neutron Scattering [1]. The instrument has been in continuous operation since 2014 and is currently available to the Australian research community for around 200 days a year. The applications of the inelastic neutron scattering techniques are diverse, ranging from the study of crystal field splitting and phonons in crystals through to the study of atomic diffusion. A range of wavelength options are available on PELICAN from 2.73 < λ < 5.97 Å providing corresponding energy resolutions in the range 0.6 < FWHM < 0.065 meV. Using appropriate phasing of the two choppers also provides additional wavelength harmonics, providing versatility without the need to reconfigure the instrument. Recent improvements to the instrument include the option to utilise polarised neutrons, in situ gas-loading for hydration experiments, and high temperature (up to 1600oC) capabilities. We have also designed and tested some custom-made quartz sample holders for ion diffusion studies in corrosive liquids. Future developments will allow use of a high-field magnet (< 7 T) on PELICAN as well as implementation of the software MANTID for data treatment and analysis.

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